1. Field of the Invention
The present invention relates to the treatment of adiponitrile and in particular to a process for reducing the amount of basic impurities in crude adiponitrile especially adiponitrile obtained from adipic acid and ammonia.
2. Description of the Prior Art
Adiponitrile obtained from adipic acid contains impurities, some of which boil at temperatures close to the boiling point of adiponitrile. 2-Cyanocyclopentylideneimine, (CPI), is an example of such an impurity. Close boiling impurities frequently cannot be removed efficiently in industrial scale distillation columns and lead to impurities in subsequent derivatives, in particular in hexamethylene diamine, that are difficult to remove. Failure to remove these latter impurities may result in inferior and variable properties, especially in polymers manufactured using such impure hexamethylene diamine. Some techniques for the purification of adiponitrile are known in the art. For example, adiponitrile may be treated with a solid acidic catalyst in the presence of water and at a temperature of at least 140.degree. C. to remove 2-cyanocyclopentylideneimine from the adiponitrile as described in Canadian Pat. No. 912,036 of B. J. Kershaw, issued Oct. 10, 1972.